WP 00/09505 discloses a colorless amorphous product of N-[1-butyl-4-[3-[3-(hydroxy)propoxy]phenyl]-1,2-dihydro-2-oxo-1,8-naphthyridin-3-yl]-N′-(2,6-diisopropyl-4-amino-phenyl)urea hydrochloride having an acyl-CoA: cholesterol acyl transferase (ACAT) inhibitory activity and being useful as an agent for treatment of hyperlipidemia and/or atherosclerosis.